Credit

Caption

Cygnus X-1 star. Negative optical image of the star (arrowed) associated with the X-ray source Cygnus X-1, thought to contain a black hole. Black holes are areas of space where the gravitational field is so strong that light cannot escape. It is thought Cygnus X-1 contains a black hole in mutual orbit with a larger companion star. This system emits X-rays as gas pulled from the star is accelerated and heated as it is sucked into the hole. Cygnus X-1 lies around 82,000 light years from Earth in the constellation Cygnus.